269 lines
6.3 KiB
Python
269 lines
6.3 KiB
Python
"""
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aiosched: Yet another Python async scheduler
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Copyright (C) 2022 nocturn9x
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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https:www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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from collections import deque
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from abc import ABC, abstractmethod
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from typing import Any
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from aiosched.errors import SchedulerError
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from aiosched.internals.syscalls import (
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suspend,
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schedule,
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current_task,
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)
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class Event:
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"""
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An asynchronous, non thread-safe event
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"""
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def __init__(self):
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"""
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Object constructor
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"""
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self.set = False
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self.waiters = set()
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def reset(self):
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"""
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Resets the event's state
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"""
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self.__init__()
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async def trigger(self):
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"""
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Sets the event, waking up all tasks that called
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wait() on it
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"""
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if self.set:
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raise SchedulerError("The event has already been set")
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self.set = True
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for waiter in self.waiters:
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await schedule(waiter)
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async def wait(self) -> Any:
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"""
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Waits until the event is set
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"""
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self.waiters.add(await current_task())
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await suspend() # We get unsuspended by trigger()
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class Queue:
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"""
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An asynchronous FIFO queue. Not thread safe
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"""
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def __init__(self, maxsize: int | None = None):
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"""
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Object constructor
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"""
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self.maxsize = maxsize
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# Stores event objects for tasks wanting to
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# get items from the queue
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self.getters = deque()
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# Stores event objects for tasks wanting to
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# put items on the queue
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self.putters = deque()
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self.container = deque()
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def __len__(self):
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"""
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Returns the length of the queue
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"""
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return len(self.container)
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def __repr__(self) -> str:
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return f"{type(self).__name__}({f', '.join(map(str, self.container))})"
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async def __aiter__(self):
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"""
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Implements the asynchronous iterator protocol
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"""
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return self
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async def __anext__(self):
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"""
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Implements the asynchronous iterator protocol
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"""
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return await self.get()
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async def put(self, item: Any):
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"""
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Pushes an element onto the queue. If the
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queue is full, waits until there's
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enough space for the queue
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"""
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if not self.maxsize or len(self.container) < self.maxsize:
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self.container.append(item)
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if self.getters:
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await self.getters.popleft().trigger(self.container.popleft())
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else:
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ev = Event()
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self.putters.append(ev)
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await ev.wait()
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self.container.append(item)
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async def get(self) -> Any:
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"""
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Pops an element off the queue. Blocks until
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an element is put onto it again if the queue
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is empty
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"""
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if self.container:
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if self.putters:
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await self.putters.popleft().trigger()
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return self.container.popleft()
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else:
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ev = Event()
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self.getters.append(ev)
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return await ev.wait()
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async def clear(self):
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"""
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Clears the queue
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"""
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self.container.clear()
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async def reset(self):
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"""
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Resets the queue
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"""
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await self.clear()
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self.getters.clear()
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self.putters.clear()
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class Channel(ABC):
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"""
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A generic, two-way, full-duplex communication channel
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between tasks. This is just an abstract base class and
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should not be instantiated directly
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"""
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def __init__(self, maxsize: int | None = None):
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"""
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Public object constructor
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"""
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self.maxsize = maxsize
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self.closed = False
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@abstractmethod
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async def write(self, data: str):
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"""
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Writes data to the channel. Blocks if the internal
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queue is full until a spot is available. Does nothing
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if the channel has been closed
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"""
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return NotImplemented
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@abstractmethod
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async def read(self):
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"""
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Reads data from the channel. Blocks until
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a message arrives or returns immediately if
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one is already waiting
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"""
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return NotImplemented
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@abstractmethod
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async def close(self):
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"""
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Closes the memory channel. Any underlying
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data is left for other tasks to read
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"""
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return NotImplemented
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@abstractmethod
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async def pending(self):
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"""
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Returns if there's pending
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data to be read
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"""
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return NotImplemented
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class MemoryChannel(Channel):
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"""
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A two-way communication channel between tasks.
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Operations on this object do not perform any I/O
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or other system call and are therefore extremely
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efficient. Not thread safe
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"""
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def __init__(self, maxsize: int | None = None):
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"""
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Public object constructor
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"""
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super().__init__(maxsize)
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# We use a queue as our buffer
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self.buffer = Queue(maxsize=maxsize)
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async def write(self, data: str):
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"""
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Writes data to the channel. Blocks if the internal
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queue is full until a spot is available. Does nothing
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if the channel has been closed
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"""
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if self.closed:
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return
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await self.buffer.put(data)
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async def read(self):
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"""
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Reads data from the channel. Blocks until
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a message arrives or returns immediately if
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one is already waiting
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"""
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return await self.buffer.get()
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async def close(self):
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"""
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Closes the memory channel. Any underlying
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data is left for other tasks to read
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"""
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self.closed = True
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async def pending(self):
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"""
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Returns if there's pending
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data to be read
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"""
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return bool(len(self.buffer))
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